martes, 29 de junio de 2010

We are pleased to present this 14th edition of Joslin's Diabetes Mellitus. This textbook continues to evolve and address the newest and most important insights into this very old but very challenging disease. Indeed, as this book goes to press, despite multiple medical and scientific advances, we are facing a worldwide epidemic of diabetes. This involves a steady increase in type 1 diabetes and almost an exponential increase in type 2 diabetes. The latter is accompanied by a parallel increase in obesity, the metabolic syndrome, and other closely related disorders. Thus we are at a fascinating point in the evolution of diabetes and a fascinating point in the evolution of a book devoted to this disease. The first edition of the Joslin textbook was published in 1916, a single-handed contribution by a man of extraordinary dedication, vision, and energy, Dr. Elliott P. Joslin. Dr. Joslin began his practice in 1898 in the pre-insulin era, and in this setting, developed a unique understanding of the natural history of diabetes. This perspective was clearly evident in the first edition, which was published some five years before the discovery of insulin by Banting, Best, Macleod, and Collip.

"There comes a point in your life when you realize who matters, who never did, who won't anymore, and who always will. So don't worry about people from your past, there's a reason they didn't make it to your future"

Food or calorie restriction has been shown in many short-lived animals and the rhesus monkey to prolong life-span. Life-long nutrition studies are not possible in humans because of their long survival. Studies over two to six years in healthy adult humans have, however, shown that a 20% reduction in food or calorie intake slows many indices of normal and disease-related aging. Thus, it is widely believed that long-term reduction in calorie or food intake will delay the onset of age-related diseases such as heart disease, diabetes and cancer, and so prolong life.

Over the last 20 or more years there has been a progressive rise in food intake in many countries of the world, accompanied by a rising incidence of obesity. Thus our increasing food and calorie intake has been linked to the rising incidence of cardiovascular disease and diabetes in early adult life. It is accepted that overeating, accompanied by reduced physical exercise, will lead to more age-related diseases and shortening of life-span. The answer is to reduce our calorie intake, improve our diet, and exercise more. But calorie restriction is extremely difficult to maintain for long periods. How then can we solve this problem?

Edited by a team of highly distinguished academics, this book provides the latest information on the beneficial effects of calorie restriction on health and life-span. This book brings us closer to an understanding at the molecular, cellular and whole organism level of the way forward.

Tobacco products are deeply ingrained in our culture, customs, and habits. "Nicotine" provides the facts about tobacco use among teenagers and offers young readers the facts about one of the most prevalent and addictive drugs in the United States. Learn how nicotine addiction has become so widespread and why it is now viewed as a public health crisis.

There is no current standard UK definition of hypertension in children. However, the issue has been researched in some detail in America were a working group in 2004 defined the condition as an average systolic and/or diastolicblood pressure≥95th percentile for gender, age and height on 3 or more separate occasions.1The working group also introduced the concept of 'pre-hypertension' which it defines as a blood pressure level ≥90th percentile but <95th percentile.

As with adults, blood pressure is a variable parameter in children. It varies between individuals and within individuals from day to day and at various times of the day. Attention must be paid to correct technique in measuring blood pressure and with small patients this includes the use of a small cuff. The traditional method of auscultation of 1st and 5th Korotkoff sounds, using a mercury sphygmomanometer, gives an accuracy that is second only to direct cannulation of the artery. Nowadays mercury and aneroid instruments are being replaced by electronic or Doppler devices.

White coat hypertension and masked hypertension may be particularly relevant in this patient group. One study found that ambulatory blood pressure measurement correlated quite well with home monitoring2and the latter is becoming a validated method.3Whatever method is used, the instrument must be regularly checked for accuracy and serviced and used correctly.

Epidemiology

A Department of Health Survey for England in 1996 showed that the mean systolic blood pressure for both boys and girls aged 5 to 15 was 111 mmHg.4Mean diastolic pressure was 57 mmHg in boys and 58 mmHg in girls. Mean pulse pressure was 58 mmHg in both boys and girls aged 5 to 15.

Blood pressure increases with age in childhood and children who are either heavier or taller or both have higher blood pressure than smaller children of the same age.5The relationship between body mass and blood pressure in children is stronger than in adults and children who have high blood pressure and are taller and heavier than their peers are more likely to become hypertensive as adults.6

Hypertension is on the increase due to the rise inobesity in children. One study found that organ damage, such asleft ventricular hypertrophy, thickening of the carotid vessel wall, retinal vascular changes and even subtle cognitive changes, were detectable in children and adolescents with high blood pressure and the authors of this study considered that hypertension was a common long-term health problem in this age group.7

Risk factors

In the absence of overt disease that will cause hypertension, there are a number of factors known to affect blood pressure in children and young adults. These are:

Salt intake- this is very important and targets to reduce our intake may not go far enough.8Processed and convenience foods tend to be very high in salt.

Obesity- childhood obesity increases the risk of childhood hypertension. The Bogalusa Heart Study derived figures from several national studies and found that the odds ratios in obese children were 2.4 for raised diastolic blood pressure and 4.5 for raised systolic blood pressure.9

Low birth weight- this seems to be a particular risk factor in patients who subsequently have a high BMI.10,11

Ask about diet, looking for high salt intake and possibly high consumption of liquorice

Examination

Examination of the child starts with looking at the general state of nutrition and apparent state of health. Check height and weight against centile charts.

Examination of the pulse precedes measurement of blood pressure. The child should be seated and relaxed or supine if a baby. The cuff is on the right arm at the level of the heart. The rubber blade inside the cloth cover should be long enough to encircle the arm and wide enough to cover approximately ¾ of the distance from shoulder to elbow. Examine the rest of the cardiovascular system. Check for displacement of the apex beat and signs of left ventricular hypertrophy.Heart murmurs in childrenmay be very relevant. Also feel the pulses in the lower limbs. If the amplitude of the pulse is poor this suggests coarctation of the aorta.

Look for stigmata of specific diseases:

Café au lait spots may suggest pheochromocytoma.

Examination of the abdomen will reveal a mass in Wilms' tumour andabdominal bruitmay suggest coarctation or other vascular abnormalities including in the renal system.

In general, the younger the child and the higher the blood pressure the greater the chance of identifying the cause. 80% are due to renal parenchymal abnormality. The table gives the order of frequency of the various causes of hypertension in 4 age groups:12

Most adults are deemed to have essential hypertension and little or no further investigation is undertaken but in children a cause for the hypertension should be sought. Basic screening tests to detect underlying pathology should be carried out together with investigations to assess co-morbidity and end organ damage. Further testing may be required, depending on individual and family histories, the presence of risk factors and the results of the screening tests.

There are no consensus UK guidelines on the management of hypertension in children. American guidelines suggest that lifestyle modifications should be applied to all hypertensive paediatric patients and that drugs are indicated in patients who fail to respond to lifestyle measures or have secondary hypertension, symptomatic hypertension, co-morbidity or end-organ damage.

This includes weight control, encouragement of exercise, reduction in dietary sodium and fat and, where appropriate, cessation of smoking and alcohol.

Drugs

American guidelines suggest starting with one drug and increasing the dose until a therapeutic effect is achieved or side-effects develop, at which point a second drug should be added. There is little experience in using combination drugs in children. There is little comparative evidence so the choice of drug depends on the physician's preference plus any secondary causes or comorbidities.

ACE inhibitorsandcalcium channel blockers- these are gradually gaining preference as first-line drugs in view of their low side-effect profile. Caution may need to be exerted when using ACE inhibitors in patients with renal disease but they can be helpful in some cases.

Angiotensin receptor antagonists- their role is currently being evaluated.14One study found that the blood pressure reduction of angiotensin- converting enzyme inhibitors, angiotensin II receptor antagonists and calcium-channel blockers was almost identical. In children with pathological proteinuria, angiotensin- converting enzyme inhibitors or angiotensin II antagonists were superior to calcium-channel blockers.15

Management of a hypertensive crisis

An acutehypertensive crisismay be the result of an acute illness, such asglomerulonephritisoracute renal failure, drugs or psychogenic substances, or exacerbation of moderate hypertension. A hypertensive crisis can present with features ofcerebral oedema, seizures, heart failure,pulmonary oedema, or renal failure. The accurate assessment of blood pressure is essential when a patient has a seizure, particularly when noepilepticdisorder is known. Anticonvulsant drugs are ineffective to treatconvulsionsin a hypertensive crisis. Suitable drugs includenifedipine,labetaloland sodiumnitroprusside. Newer rapid-acting drugs such as clevidipine have been developed.16The aim is to decrease blood pressure to normal within several hours. Close supervision is required to avoid an excessively rapid decrease in blood pressure that may result in underperfusion.17A Cochrane review concluded that further research was needed to determine which drugs were best for the treatment of hypertensive crisis and their effect on morbidity and mortality.18

Prognosis

This is dependent upon the underlying cause. Experience from adults shows that poorly controlled blood pressure is a risk factor for CHD and is the major risk factor for stroke. There is no definitive data to link childhood blood pressure withcardiovascular riskbut extrapolation of other data would suggest that, if hypertension is poorly controlled from an early age, morbidity or mortality will also strike early.12,19